Drawing on a lively recent historiography stimulated by the fall of the Soviet Union, this chapter considers various ways in which Russia/USSR can be regarded as an empire and goes on to explore the relationships between Russians and the myriad other ethnic groups within the Empire’s borders. After showing how those borders expanded and contracted between 1552 and 1991, the chapter discusses the resultant territorial integration and demographic intermingling. The bulk of the chapter concentrates on four fundamental shifts that changed the way Russia’s rulers and elites viewed the Empire’s diversity and rationalized imperial rule between the sixteenth and twentieth centuries. Arguing that authorities viewed the Empire and its population through four successive ideological lenses—Christian, civilizational, nationalist and Marxist—the chapter concludes by suggesting that the post-Soviet Russian Federation remains an empire, or at least that its imperial legacy remains crucial to its identity.